如何在大量计算过程中使屏幕停止冻结？

Question

好的，我要做的是改变某个图像的像素数据。我想使用一个UIView，每次它作为progressbar循环时都会向右移动。然而，现在的情况是，屏幕在计算过程中冻结，在计算完成之前不会发生任何事情。状态栏时钟也不会更新。有没有办法将这些计算移到背景中，并且仍然使用屏幕不动产？

func lock() {

    let lockView =  UIImageView(image: self.photoBackgroundView.image!)
    var progressBar = UIView(frame: CGRectMake(-self.view.width,0,self.view.width,20)
    let increment = progressBar.width/self.photoBackgroundView.width
    var password = self.textField.text!
    if password == "" {
        password = " "
    }
    var currentIndex = 0



    let imageRect = CGRectMake(0, 0, self.photoBackgroundView.image!.size.width,self.photoBackgroundView.image!.size.height)

    UIGraphicsBeginImageContext(self.photoBackgroundView.image!.size)
    let context = UIGraphicsGetCurrentContext()

    CGContextSaveGState(context)
    CGContextDrawImage(context, imageRect, self.photoBackgroundView.image!.CGImage)
    for x in 0...Int(self.photoBackgroundView.image!.size.width) {
        print(x)

        progressBar.frame.origin.x += (CGFloat(x) * increment)
        self.view.addSubView(progressBar)


        for y in 0...Int(self.photoBackgroundView.image!.size.height) {
            let pointColor = lockView.layer.colorOfPoint(CGPoint(x: x, y: y))

            if currentIndex == Array(password.characters).count {
                currentIndex = 0
            }
            let red = encrypt(pointColor.components.red, passwordChar: Array(password.characters)[currentIndex], currentIndex: currentIndex, x: x, y: y)
            currentIndex++
            if currentIndex == Array(password.characters).count {
                currentIndex = 0
            }
            let green = encrypt(pointColor.components.green, passwordChar: Array(password.characters)[currentIndex], currentIndex: currentIndex, x: x, y: y)
            currentIndex++
            if currentIndex == Array(password.characters).count {
                currentIndex = 0
            }
            let blue = encrypt(pointColor.components.blue, passwordChar: Array(password.characters)[currentIndex], currentIndex: currentIndex, x: x, y: y)
            currentIndex++

            CGContextSetRGBFillColor(context, red, green, blue, pointColor.components.alpha)
            CGContextFillRect(context, CGRectMake(CGFloat(x), CGFloat(y), 1, 1))

        }



    }

    CGContextRestoreGState(context)
    let newImage = UIGraphicsGetImageFromCurrentImageContext()
    self.photoBackgroundView.image = newImage
    self.slideView.addSubview(photoBackgroundView)
    self.view.addSubview(self.slideView)
}

Answer 1

当你在主线程中进行繁重的计算时，你的屏幕或用户界面冻结了。主线程负责更新UI元素，当您在主线程上执行繁重的工作时，它将阻止主线程并冻结UI，这是不推荐的。

默认情况下，您编写的任何代码都将在主线程上运行。您需要分别在后台线程中编写代码，以便主线程和BGthread可以同时运行。

您可以使用NSOperationQueue或GCD（Grand Central Dispatch）轻松编写要在其他一些后台线程中运行的函数。

请点击此链接进行进一步解释。

Answer 2

您可以在后台线程中进行这些计算。

Swift 2：

let priority = DISPATCH_QUEUE_PRIORITY_DEFAULT
dispatch_async(dispatch_get_global_queue(priority, 0)) {
    // Put the calculations here
    dispatch_async(dispatch_get_main_queue()) {
        // any updates of the UI need to be here which will be executed in the main thread after your background task completes. For example adding subviews
    }
}

Swift 3：

看这个答案